1. Field of the Invention
The present invention relates to a floating caliper-disc type brake.
2. Related Art
A floating caliper-disc type brake comprises a support fixed to non-rotatable portion of a vehicle, a caliper floatably supported by the support and an inner pad to be brought into contact with a piston which is slidably engaged in a cylinder formed in a rear arm of the caliper, an outer pad supported by a front arm of the caliper, wherein a disc rotating together with a wheel is clamped by the inner and outer pads to generate a breaking torque. In the disc brake of this type, a gap between the disc and each pad, when the brake is released, is assured in the following manner. That is, a seal ring composed of rubber elastic body is interposed between the cylinder and the piston, wherein when the brake is applied, the piston is allowed to move in one direction to protrude from the cylinder owing to elastic deformation of the seal ring, and when the brake is released, the piston is moved in the other direction to return to be pushed into the cylinder owing to elastic restoration to the original form of the seal ring. When both pads are worn, the seal ring is gradually varied in its retaining position with respect to the piston depending on wearing amount of both pads so that the piston is gradually moved in one direction to protrude from the cylinder. Consequently, amount of depression of a brake pedal, namely, amount of brake operating liquid is kept constant and a given gap is defined between the disc and the inner pad. When the outer pad is kicked back by the rotating disc, the outer pad is moved together with the caliper so as to be kept away from the disc, thereby defining a gap between the disc and the outer pad, at the time of release of the brake. At this time, caliper slightly floats relative to the support.
However, in such a conventional floating caliper-disc type brake, a given gap between the disc and the inner pad is surely defined by the elastic deformation of the seal ring. However, there is a tendency that a gap between the disc and the outer pad is not surely defined. Accordingly, dragging torque is always generated when the outer pad is slid with respect to the disc during the traveling of the vehicle, which causes the problems of increase of fuel consumption of the vehicle and generation of different noise (jar) involved in sliding of the outer pad with respect to the disc. The more the manufacturing and attaching accuracy is improved, the more such problem occur.